The traditional method for retracting gingival tissue prior to the taking of an impression of a prepared tooth to form a crown or bridge is to mechanically pack a small length of cord saturated with or without an astringent about the base of the tooth to enlarge the gingival sulcus or space about the base of a tooth. After a period of time, the cord is removed from the enlarged space defined about the base of the tooth. Upon the removal of the cord, it frequently happens that coagulum formed to stop the bleeding or seepage of fluid is removed with the cord to result in the seepage of additional bleeding into the space. As a result, an impression cannot be made of the prepared tooth until the additional bleeding can be controlled or stopped. Thus, the traditional procedure for enlarging the space between the gum and the base of the tooth necessary for taking an accurate impression is tedious, time consuming, and painful or extremely uncomfortable for the patient. Also, there exists the danger that the dentist may accidentally force the cord beyond the physiologic limit of the space to create a potential periodontal pocket which can cause the tooth to eventually be lost. The general practice of using the cord technique is relatively difficult and tedious for the dentist.
In the event that the space between the tooth and the gum that has to be retracted is very small, it becomes even more difficult for the dentist to place the cord without injuring the gum tissue and from forcing the cord beyond the physiologic limit, rendering the procedure more painful for the patient. Further, the placing of the cord is not a procedure which the dentist may delegate to a dental assistant or dental hygienist. Also, the packing of a retraction cord is a most disliked step to in performing a crown or bridge restoration procedure.
Efforts have been made to obviate the noted disadvantages of affecting the retraction of the gingival tissue by the use of a cord. One such known effort is the use of a kaolin clay type material that is mixed with an astringent salt which is simply placed about a prepared tooth to absorb the moisture to cause the gum tissue to shrink. Such a product is marketed by Sybron Dental Specialties under the trademark or brand name ExpaSyl.
It has been noted that such kaolin type material is packaged in a cartridge similar to a typical anesthetic cartridge commonly used in a dental office that requires the cartridge to be used with a syringe. The end of the cartridge is pierced with a needlelike cannula and the force of the syringing pressure is required to extrude the clay like kaolin material through the cannula. Because of the density of the kaolin type material, the cannula requires the opening to be very large so as to enable the kaolin type material to flow therethrough. The large gauge opening of the cannula renders the bending of the cannula difficult and which bending is often required in order to place the material in difficult to reach places within a patient's mouth. Because the opening of the cannula is quite large, difficulty is encountered in placing the kaolin type material about the gingival sulcus in a manner similar to the traditional method of packing cord to retract the gum tissue.
Also, the use of such kaolin type material to retract the gum tissue often results in crumbling of the kaolin material, rendering it difficult to place in the space between the gum tissue and the tooth to attain the desired retraction of the gum tissue. Another noted problem with such kaolin type material is the removal of the kaolin material after the period of time required to affect the hemostatic action or retraction. Generally, the kaolin material is required to be washed out using a water-air spray with extreme care to remove all the kaolin material without restarting any bleeding in the gingival sulcus.
Another known technique for effecting a non-cord retraction and/or hemostatic is disclosed in U.S. Pat. No. 5,676,543. Therein disclosed is a generally two part process utilizing two different viscosities of a silicone material to effect the cordless retraction and/or hemostatic of the gingival sulcus.
Also, U.S. Pat. No. 6,890,177 discloses a more simplified cordless retraction method and device whereby the cordless retraction may be accomplished by resorting to a porous sponge or foam cellular dam which is shaped to conform with the prepared tooth or teeth, arranged to contain a two part silicone type impression material that includes a base portion and a catalyst, whereby the patient's biting force is utilized to apply the necessary pressure to effect the desired retraction.
Other devices and methods are used to retract the gingival sulcus. One product is sold under the trademark Magic FoamCord which is dependent upon an expanding vinyl polysiloxane or silicone material which is a two-part, chemically cured component system that are required to be mixed by the dentist at chair side prior to application and which cures or sets to effect the retraction of the gingival tissue.